A new model for simple neural nets and its application in the design of a neural oscillator

The results of a previous theoretical study of a class of systems are applied for the design of neural nets which try to simulate biological behavior. Besides the models for single aperiodic and periodic neurons, a “neural oscillator” is developed which consists of two cross-excited neurons. Its response is similar to the firing pattern of certain biological neural oscillators, like the flying system of the locust. Also, by proper change of its parameters, it can be made highly irregular, providing a deterministic model for the spontaneous neural activity.     

Common STAT3 variants are not associated with obesity or insulin resistance in female twins

In animal models, STAT3 action in the hypothalamus and liver appears essential for normal body weight and glucose homeostasis in response to insulin. We hypothesized that variation in the STAT3 gene may be associated with body fat and/or insulin resistance in the general population. Five tagging SNPs spanning the STAT3 gene, rs8074524, rs2293152, rs2306580, rs6503695, and rs7211777 were genotyped in 2776 white female twins (mean age, 47.4+/-12.5 yrs) from the St Thomas' United Kingdom Adult Twin Registry (Twins UK). Minor allele frequencies were as follows: rs8074524 (0.19), rs2293152 (0.37), rs2306580 (0.06), rs6503695 (0.35), and rs7211777 (0.34). The minor allele of rs2293152 was associated with higher homeostasis model assessment index of insulin resistance (p=0.013) in the full cohort and confirmed in sib-transmission/disequilibrium test (TDT): (p=0.015; n=60). However, there were no associations with fasting serum insulin or glucose or with obesity variables. Although defective STAT3 action results in obesity and insulin resistance in animal models, we failed to establish any indicative associations with common SNPs in this human study.     

Efficacité et innocuité du prélèvement percutané de sperme testiculaire dans la prise en charge de l’infertilité masculine

Objective

To assess the efficacy and safety of percutaneous testicular biopsy to provide sperm cells for ICSI in male patients with azoospermia not amenable to surgical treatment.

Materials and methods

From October 1995 to December 2001, 175 biopsies were performed in men with azoospermia to provide material for intracytoplasmic sperm injection. Azoospermia was obstructive (OA) in 41 cases and non-obstructive (NOA) in 134 cases. Open biopsy was performed in the first 15 patients in the series and percutaneous biopsy was performed on an outpatient basis, under local anesthesia, with a Biopty Gun® (14G needle), in the subsequent patients as the first step in management. Open surgical biopsies were performed in another 15 patients following a sperm cell-negative percutaneous biopsy.

Results

All biopsies performed for OA were positive, but only 51/134 biopsies (38%) were positive in the NOA group. The material provided by percutaneous biopsy, when positive for sperm cells, was always sufficient to perform ICSI. When percutaneous biopsy was negative, open surgical biopsy failed to give better results. Five men developed minor complications (acute hematocele) following percutaneous biopsies requiring reoperation for hemostasis (3.12%). No major complications were observed. Results were comparable in terms of fertilization and pregnancy rates whether fresh or frozen-thawed sperm was used.

Conclusion

Percutaneous testicular sperm extraction is a safe, well-tolerated and cost-effective procedure in the management of male-factor infertility related to azoospermia.     

Numerical simulation of cardiovascular dynamics with different types of VAD assistance

A variety of methods by which mechanical circulatory support (MCS) can be provided have been described. However, the haemodynamic benefits of the different methods have not been adequately quantified. The aim of this paper is to compare the haemodynamic effects of six forms of MCS by numerical simulation. Three types of ventricular assist device (VAD) are studied: positive displacement; impeller and a novel reciprocating-valve design. Similarly, three pumping modes are modelled: constant flow; counterpulsation and copulsation. The cardiovascular system is modelled using an approach developed previously, using the concentrated parameter method by considering flow resistance, vessel elasticity and inertial effects of blood in individual conduit segments. The dynamic modelling of displacement and impeller pumps is represented by VAD inlet/outlet flow-rate changes. The dynamics of the reciprocating-valve pump is modelled with a specified displacement profile. Results show that in each simulation, the physiological variables of mean arterial pressure and systemic flow are adequately maintained. Modulation of the impeller pump flow profile produces a small (5 mmHg) oscillatory component to arterial pressure, whereas the displacement and reciprocating-valve pumps generate substantial arterial pressure and flow pulsatility. The impeller pump requires the least power input, the reciprocating valve pump slightly more, and the displacement pump the most. The in parallel configuration of the impeller and displacement pump designs with respect to the left ventricle provides near complete unloading and can cause the aortic valve to remain closed throughout the entire cardiac cycle with the attendant risk of aortic valve leaflet fusion following prolonged support. The in series configuration of the reciprocating-valve pump avoids this shortcoming but activation must be carefully synchronized to the cardiac cycle to allow adequate coronary perfusion. The reciprocating-valve pump is associated with haemodynamic advantages and a favourable power consumption.     

Local tissue temperature increase of a generic implant compared to the basic restrictions defined in safety guidelines

The objective of this study was to investigate if persons with implantable medical devices are intrinsically protected by the current electromagnetic safety guidelines. For inter-laboratory comparisons, the U.S. Food and Drug Administration has defined a generic implant as consisting of an insulated wire with noninsulated tips, simulating active implants composed of a metallic case, and insulated wires with electric contacts at the tip. In this study, we determined the amplitude of the uniform electric fields induced in body tissues that cause a local increase in the tissue temperature by 1 °C in the presence of this generic implant for a wide range of frequencies and wire lengths. The field amplitudes were compared to the basic restrictions of the current exposure guidelines for both occupational and uncontrolled exposure. Results showed that a 1 °C temperature increase in the tissues around the tips of the generic implant can be reached for field strengths much smaller than 1% of those in the basic restrictions. The simulated results were validated by experimental evaluations. The impact of perfusion was investigated and was found to lead to a reduction in the local temperature peak by only 1.6-3 times. Additional simulations inside an inhomogeneous anatomical model were performed to ascertain whether similar heating as in the generic model was observed. The significant temperature elevations due to the presence of a generic implant indicate that demonstrating compliance with the basic restrictions might not be sufficient for persons with implants. Special considerations may be required, especially in the case of novel, emerging technologies that feature strong near-fields at frequencies below 10 MHz (e.g., wireless power-transfer systems).     

TissuePatch™ as a novel synthetic sealant for repair of superficial lung defect: in vitro tests results

Controversies surrounding the efficacy of surgical sealants against alveolar air leaks (AAL) in lung surgery abound in the literature. We sought to test the sealing efficacy of a novel synthetic sealant, TissuePatch? in an in vitro lung model. The lower lobe of freshly excised swine lung (n?=?10) was intubated and ventilated. A superficial parenchymal defect (40?×?25 mm) was created, followed by AAL assessment. After sealant application, AAL was assessed again until burst failure occurred. The length of defect was recorded to evaluate the elasticity of the sealant. Superficial parenchymal defects resulted in AAL increasing disproportionally with ascending maximal inspiratory pressure (Pmax). Multiple linear regression analysis revealed strong correlation between AAL and Pmax, compliance, resistance. After sealant application, AAL was sealed in all ten tests at an inspired tidal volume (TVi) of 400 ml, in nine tests at TVi?=?500 ml, in seven at TVi?=?600 ml and in five at TVi?=?700 ml. The mean burst pressure was 42?±?9 mBar. Adhesive and cohesive sealant failures were found in six and three tests respectively. The length of defect before sealant failure was 8.9?±?4.9% larger than that at TVi?=?400 ml, demonstrating an adequate elasticity of this sealant film. TissuePatch? may be a reliable sealant for alternative or adjunctive treatment for repair of superficial parenchymal defects in lung surgery. The clinical benefits of this sealant should be confirmed by prospective, randomised controlled clinical trials. Die Wirksamkeit von chirurgischen Klebstoffen zur Prävention von alveolo-pleuralem Luftleck (APL) ist trotz zunehmenden klinischen Anwendungen in Lungenchirurgie immer noch kontrovers diskutiert. Wir evaluierten die Abdichtungswirksamkeit von einem neuartigen synthetischen Kleber, TissuePatch? mittels eines in vitro Lungenmodels. Der Unterlappen von frisch entnommenen Schweinlungen (n?=?10) wurde intubiert und beatmet. Eine pleurale Läsion (40?×?25 mm) wurde erstellt und APL mit steigendem inspiratorischem Tidalvolumen (TVi) untersucht. Nach Applikation von TissuePatch? wurde APL auf die gleiche Weise gemessen bis zur Auftritt von Kleberbruch. Zur Untersuchung der Elastizität des Klebers wurde die Länge der pleuralen Läsion gemessen. Pleurale Läsion führte bei aufsteigendem maximalem inspiratorischem Druck (Pmax) zu überproportionalem Anstieg von APL. Multiple lineare Regressionsanalyse ergab eine starke Korrelation zwischen APL und Pmax, Lungencompliance sowie Widerstand. Nach der Applikation von Klebstoff wurde APL bei TVi?=?400 ml in allen zehn Testen versiegelt, bei TVi?=?500 ml in neun Testen, bei TVi?=?600 ml in sieben und bei TVi?=?700 ml in fünf Testen. Der mittlere Pmax, der zu Kleberbruch führte, betrug 42?±?9 mBar. Bei den Versuchen wurden adhäsiver und kohäsiver Kleberbruch in jeweils sechs und drei Testen gefunden. Die Länge der pleuralen Läsion vor dem Kleberbruch war 8,9?±?4,9% größer als die bei TVi?=?400 ml. Unsere Versuche zeigten eine zuverlässige Versiegelung von TissuePatch? unter mechanischer Ventilation. Die klinische Nützlichkeit vom Kleber als unterstützende Maßnahme zur Prävention von alveolo-pleuralem Luftleck in Lungenchirurgie sollte durch prospektive, randomisierte kontrollierte klinische Studien bestätigt werden.     

Acute T3 treatment protects the heart against ischemia-reperfusion injury via TRα1 receptor

We have previously shown that acute thyroid hormone treatment could limit reperfusion injury and increase post-ischemic recovery of function. In the present study, we further explore potential initiating mechanisms of this response. Thus, isolated rat hearts were subjected to 30 min zero-flow global ischemia (I) followed by 60-min reperfusion (R). Reperfusion injury was assessed by post-ischemic recovery of left ventricular developed pressure (LVDP%) and LDH release. T3 at a dose of 60 nM which had no effect on contractile function of non-ischemic myocardium, significantly increased LVDP% [48% (2.9) vs. 30.2% (3.3) for untreated group, P < 0.05] and reduced LDH release [8.3 (0.3) vs. 10 (0.42) for untreated group, P < 0.05] when administered at R. T4 (60 and 400 nM) had no effect on contractile function either in non-ischemic or ischemic myocardium. Administration of debutyl-dronedarone (DBD), a TRα1 antagonist abolished the T3-limiting effect on reperfusion injury: Thus, co-administration of T3 and DBD resulted in significantly lower LVDP%, [23% (4.7) vs. 48% (2.9) for T3 group, P < 0.05] and higher LDH release [9.9 (0.3) vs. 8.3 (0.3), for T3 group, P < 0.05]. In conclusion, acute T3 and not T4 treatment will be able to protect against reperfusion injury. T3 can exert this beneficial effect on ischemic myocardium at a dose that has no effects on non-ischemic myocardium. Acute T3-limiting effect on reperfusion injury is mediated, at least in part, via TRα1 receptor.     

Design of neural nets with intermittent response and certain other relevant studies

The application of the earlier results (Pavlidis, T. 1965. “A New Model for Simple Neural Nets and its Application in the Design of a Neural Oscillator.”Bull. Math. Biophysics,27, No. 2, 215–229) to the design of more complex neural nets is attempted. The following cases are considered:

1. 1.
   Chains of neurons where it is proven that the frequency of the output pulses does not depend on the value of the input as long as it is above a certain threshold.     

A comparative chemotaxonomic study of eight taxa of the Dipsacaceae family

ABSTRACT

Eight taxa of the Dipsacaceae family were examined for their fatty acid and sterol composition. Separation and identification of the lipid fraction was achieved by gas chromatography and gas chromatography-mass spectrometry. The phenotypic differences among taxa were established by cluster analysis. Correlation coefficients were obtained to investigate numerical relationships among constituents of the fatty acids. The results showed many significant correlations between different constituents, as well as four clusters of taxa using two linkage types of clustering.